It is the box being nailed down.

Now I can hear the heavy feet tramping again along the hall, with many other idle feet coming behind them.
The door is shut, the chains rattle.

There is a grinding of the key in the lock.

I can hear the key withdrawn, then another door opens and shuts.

I hear the creaking of lock and bolt.
Hark! In the courtyard and down the rocky way the roll of heavy wheels, the crack of whips, and the chorus of the Szgany as they pass into the distance.
I am alone in the castle with those horrible women.